Musannaf Ibn Abi Shaybah

Hazrat Mak'hool says that when a Muhrim becomes junub (in a state of major ritual impurity), while pouring water over his head, he should neither rub it with his hand nor scrub it.

Hazrat Ata says that if a person in the state of Ihram performs Ghusl, he should pour water over his head as it is and should not rub it with his hand.

Hasan does not consider it objectionable for a muhrim (person in the state of ihram) to perform ghusl (ritual bath), but he dislikes excessively rubbing the head with the hand while bathing.

When Hazrat Urwah would perform ghusl in the state of ihram, he would pour water over his head but would not rub it with his hand; rather, he would only lightly wipe it (pass his hand gently over it).

Hazrat Abdul A'la (may Allah be pleased with him) says that I saw Hazrat Saeed bin Jubair performing ghusl (ritual bath) while in the state of ihram; he was pouring water over his head but was not rubbing it with his hand.